The abstract factory design pattern implemented in c# using generics., C#

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//Rextester.Program.Main is the entry point for your code. Don't change it.
//Compiler version 4.0.30319.17929 for Microsoft (R) .NET Framework 4.5

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text.RegularExpressions;

namespace Rextester
{
    public class Program
    {
        public static void Main(string[] args)
        {
            // Get the list of factories
            var factories = GetFactories();
            
            // Iterate through the list of factories, creating the instance and running a method.
            foreach(var f in  factories)
            {
                var x = f.CreateInstance();
                x.DoSomething();
            }
        }
        
        // Creates a list of IFactory with different implementations
        static List<IFactory> GetFactories()
        {
            return new List<IFactory>()
            {
                new Concrete.Factory<Concrete.A>(),
                new Concrete.Factory<Concrete.B>()
            };
        }
    }
    
    // This is the abstract factory.
    public interface IFactory 
    {
        IBase CreateInstance();
    }
    
    // This is the interface the abstract factory returns.
    public interface IBase
    {
        void DoSomething();
    }
    
}

namespace Concrete
{
    // This is a concrete implementation of the abstract factory using generics.
    // I've put it in a different namespace to make the decoupling between this and the using class very clear.
    public class Factory<T> : Rextester.IFactory where T : Rextester.IBase, new()
    {
        public Rextester.IBase CreateInstance()
        {
            return new T();
        }
    }
    
    // This is a concrete implementation of the IBase interface
    public class A : Rextester.IBase
    {
        public void DoSomething() 
        {
            Console.WriteLine("This is A");
        }
    }
    
    // This is a different concrete implementation if the IBase interface
    public class B : Rextester.IBase
    {
        public void DoSomething() 
        {
            Console.WriteLine("This is B");
        }
    }
}

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Compilation time: 0,16 sec, absolute running time: 0,08 sec, cpu time: 0,08 sec, average memory usage: 13 Mb, average nr of threads: 3